How to check validity of URL in Swift?

Question

Trying to make an app launch the default browser to a URL, but only if the URL entered is valid, otherwise it displays a message saying the URL is invalid.

How would

Answer 1

Using 'canOpenUrl' was too expensive for my use case, I found this approach to be quicker

func isStringLink(string: String) -> Bool {
    let types: NSTextCheckingResult.CheckingType = [.link]
    let detector = try? NSDataDetector(types: types.rawValue)
    guard (detector != nil && string.characters.count > 0) else { return false }
    if detector!.numberOfMatches(in: string, options: NSRegularExpression.MatchingOptions(rawValue: 0), range: NSMakeRange(0, string.characters.count)) > 0 {
        return true
    }
    return false
}

Answer 2

For a swift 3 version of the accepted answer:

func verifyUrl(urlString: String?) -> Bool {
    if let urlString = urlString {
        if let url = URL(string: urlString) {
            return UIApplication.shared.canOpenURL(url)
        }
    }
    return false
}

Or for a more Swifty solution:

func verifyUrl(urlString: String?) -> Bool {
    guard let urlString = urlString,
          let url = URL(string: urlString) else { 
        return false 
    }

    return UIApplication.shared.canOpenURL(url)
}

Answer 3

2020, I was tasked on fixing a bug of a method for underlining string links within a string. Most of the answers here don't work properly (try: aaa.com.bd or aaa.bd) These links should be valid. And then I stumbled upon the regex string for this.

Ref: https://urlregex.com/

So based on that regex

"((?:http|https)://)?(?:www\\.)?[\\w\\d\\-_]+\\.\\w{2,3}(\\.\\w{2})?(/(?<=/)(?:[\\w\\d\\-./_]+)?)?"

We can write a function.

SWIFT 5.x:

extension String {
    var validURL: Bool {
        get {
            let regEx = "((?:http|https)://)?(?:www\\.)?[\\w\\d\\-_]+\\.\\w{2,3}(\\.\\w{2})?(/(?<=/)(?:[\\w\\d\\-./_]+)?)?"
            let predicate = NSPredicate(format: "SELF MATCHES %@", argumentArray: [regEx])
            return predicate.evaluate(with: self)
        }
    }
}

OBJECTIVE-C (write this however you want, category or not).

- (BOOL)stringIsValidURL:(NSString *)string
{
    NSString *regEx = @"((?:http|https)://)?(?:www\\.)?[\\w\\d\\-_]+\\.\\w{2,3}(\\.\\w{2})?(/(?<=/)(?:[\\w\\d\\-./_]+)?)?";
    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"SELF MATCHES %@" argumentArray:@[regEx]];
    return [predicate evaluateWithObject:string];
}

Answer 4

This accepted answer doesn't work in my case with wrong url without data https://debug-cdn.checkit4team.com/5/image/Y29tbW9uL2RlZmF1bHRfYXZhdGFyLnBuZw==

So I write extension to solve

extension String {
    var verifyUrl: Bool {
        get {
            let url = URL(string: self)

            if url == nil || NSData(contentsOf: url!) == nil {
                return false
            } else {
                return true
            }
        }
    }
}

Use it:

if string. verifyUrl {
    // do something
}

Hope this help!

Answer 5

I found this one clean (In Swift):

func canOpenURL(string: String?) -> Bool {
    guard let urlString = string else {return false}
    guard let url = NSURL(string: urlString) else {return false}
    if !UIApplication.sharedApplication().canOpenURL(url) {return false}

    //
    let regEx = "((https|http)://)((\\w|-)+)(([.]|[/])((\\w|-)+))+"
    let predicate = NSPredicate(format:"SELF MATCHES %@", argumentArray:[regEx])
    return predicate.evaluateWithObject(string)
}

Usage:

if canOpenURL("abc") {
    print("valid url.")
} else {
    print("invalid url.")
}

===

for Swift 4.1:

func canOpenURL(_ string: String?) -> Bool {
    guard let urlString = string,
        let url = URL(string: urlString)
        else { return false }

    if !UIApplication.shared.canOpenURL(url) { return false }

    let regEx = "((https|http)://)((\\w|-)+)(([.]|[/])((\\w|-)+))+"
    let predicate = NSPredicate(format:"SELF MATCHES %@", argumentArray:[regEx])
    return predicate.evaluate(with: string)
}

// Usage
if canOpenURL("abc") {
    print("valid url.")
} else {
    print("invalid url.") // This line executes
}

if canOpenURL("https://www.google.com") {
    print("valid url.") // This line executes
} else {
    print("invalid url.")
}

Answer 6

This will return a boolean for a URL's validity, or nil if an optional URL with a value of nil is passed.

extension URL {

    var isValid: Bool {
        get {
            return UIApplication.shared.canOpenURL(self)
        }
    }

}

Note that, if you plan to use a Safari view, you should test url.scheme == "http" || url.scheme == "https".